Cloth water bag



y 1951 c. J. KINTNER ETAL 2,550,697

CLOTH WATER BAG Filed May 8, 1946 2 Sheets-Sheet l TIME FOR PASS/I65 0F 5'0'56 WATER l/V JECW/VDS MINUTES OF 6026 AT 3207' Z2 4 vl2iElgiTOR$ BY r. N?

ATTORNEY$ Patented May 1, 1951 iumreo cLo'rn WATER, BAG

Charles J; Kintner, Birmingham TownshimChester County, Pa and William P-.--Hall, -Wilmington, Del, .assignors to .lfoseph=Bancroft-'&--Sons Co Wilmington, Del, a corporation of Dela- Ware Application May 8, 1946, Serial No. 668,258

' This invention relates to water bags and. a process for preparing cellulose fabric for' the same.

It is general knowledge that cellulose fibers,

--whether natural, such as cotton and linen, or

whethersynthetic, such as viscose rayon, when subjected fora time to water, adsorb or absorb the-Water and-swell beyond theirnormal size.

-This degree of swelling varies with thetype of fiber, being, iorexample, less with cotton'a'ndl greater .With rlinen and, viscose rayon.

It is also known that many materials exist which have the ability of imbibing water and of lose, polyvinyl alcohol.

swelling excessively. Amongsuoh' products we may mention, for example, gum arabic, gum tragacanth, gum karaya, alginates, methyl cellu- In fact, manysubstances which ordinarily are considered inactive toward Water in this respect actually-absorb -water to a swelling is practically immeasurable.

slight extent-andswell, although sometimes this This phenomenon of slowly absorbing water has been used since early humantimes to cooldrinking water --beyond the temperature of the surrounding atmosphere. The ancients-used goat skins andlunglazed pottery jars, the latter being stillin use.

The physical principles involved consist of evaporation of water from the outside ofuthe moist bag -or--container into. the surrounding. atmosphere, the water evaporated being continually-replaceol by passage of water through. the

. container wall.

The latent heat of evaporation is furnished to someextent by .the water in the bag and this.iremovalofsheat energy from the water results in a lowering of the. temperature, thus producing Water colder than the surrounding atmosphere. The rate of evaporation, and

therefore the cooling. effect is to some extent,

other factorsbeing equal, .dependent upon; the surface available for evaporation, the greater the surface the greater .the rateoflevaporation. (To

-obtain-maximum cooling efficiency. of av water bag, it, istherefore. necessary to have .as large a surface as possible exposed to the atmosphere.

In the casezofv goat skins. andearthenware,jars,

the containerrepresents for all practical purposes H alcontinuous;.surface,,;but1 if, a woven cloth is used, 5 the surface will consist; of alternate yarns and interstices, and; will not ,be, continuous and uniformtas in a goatskin.

It isevident that theuse, of a woven cloth involves great. difiiculties since the water i would tend to leakithrough the interstices, thus causing 'a'excessive leakage, snaking the bagimpractieal. lieverthelesai ne .ba have b en madeivhic 7 c aims. (c1.. 2s-78 *5 however, are costly as compared with a-cotton bag, are susceptible-to mildew: and also; are: easily attacked :by chemicals, such as the chlorine in K purified drinking water. I

Rayon might be used-for; this purpose, but, due

10 to the-poor wet strength of thiamateriaLit-has 7 not provenpractical since great tensile forces-will be applied to the cloth when the bag is full-of water, this force being the greater the larger ql-the-bag.

v-iCotton has-been unsatisfactoryior the purpose j due to its lowdegree of-swe1ling-;--the leakage occurring being excessive even when tightlywoven yfabrics are-used.

To; make-use of; cotton, manufacturers have-rezorsorted to the application of fabric sizing materials-which, when in contactwwith water will 'swell. and prevent the excessive: passage; of;-water through the pinterstices. The materials eused wWere those. previouslymentioned, such as,;fo'rrexample, gum tragacanthcand 'methylucellulose,

, employed in conjunction with a' binder, such as, for example, acrylate resinsrwhichiact to retain Ol' hDld 'thS swelling materialzgandyprevent it from loosening from the cloth and passing-into .the weter. Theplastic material:inrthisgcaseis an'aux- ;iliary: material. However, impregnating the fab- --f1'ic with a- ;sizing; as described tendsto close the fabric andto coat the individual fibers and; yarns. wBy ,thus presenting a solid-0r continuous surface 'to the air, the, cooling-efficiencyof; the bagis decidedly less since the very large surface-, presented by the individualgunsized :fibers ,has-been markedlyreduced. Y

Wehavenow discovered that ificertaincotton 40 fabricsbetreated as hereinafter, described,;wa-

, l terbags made therefrom meet :the above requirements; and injfact possess outstanding properties, better than heretofore obtainable.

, Essentially the tdiscovery consists in partly -alterin such-fabrics by; chemical treatment,

- without destroyingthe fibrous and fabric-nature of the material, so thatewhen the cottongis brought .into contact with ,water it will-swell markedly, and close up the; interstices su fiiciently toobtain theresults without excessive leakage.

i In addition; the fabric "prepared by this process as lbeiur r s w arre ati e yemuc largensurface for evaporation The fabriohas, .;by,v irtue ofthe, treatment given-,alsoacquired a r lueble du a 'e i ta cetc m dewinaian li addition, if desired, may have flame resistance.

To accomplish the desired objective, we select a fabric of the character hereinafter described and subject it to a mineral acid, and by chemical combination introduce acid groups into the cellulose by heating (i. e. curing) the treated fabric, at a temperature and for a time suficient to bring about such chemical combination. The chemical which brings about the swelling being thus internally combined with the cellulose of the fibers, the evaporative surface of the fabric and of its yarns is retained unimpaired. Where, as in other processes, the fibers and yarns are coated, the evaporating surface of the fabric itself is reduced. We prefer to use strong acids which will combind with the cellulose and which are not excessively volatile nor produce chemicals which will detrimentally alter the character of the fibers, under the conditions of the process, such, for example, as orthophosphoric, pyrophosphoric, sulfuric, polyphosphoric, orthophosphorous and pyrophosphorous acid, salts of said acids, substitution products of said acids and anhydrides of said acids.

The anhydrides, salts and substitution products of the acids should be capable of producing the proper pH condition on the cured fabric to insure combination with the cellulose and therefore volatile salts, such as ammonia and mono substituted polyacids, are recommended as these products will produce the proper conditions on the fabric.

Among substituted acids we may mention, for example, phosphamic, sulphamic, fluorophos phonic, phenylphosphoric and phenoldisulphonic acid.

It is possible to combine other acids such as, for example, phthalic, glutaric and salicylic acids by the above process but 'the swelling obtained with such acids is not of so high a degree. We, therefore, prefer to use the strong acids listed above (which by comparison are much stronger in their effect on the cellulose) and have obtained the most desirable results with ortho or pyrophosphoric acid with urea. Since those products are inexpensive and easily available they are recommended as the most practical in large scale production.

The acids should, as already stated, be capable of combining with the cellulose under the conditions of the process, and should not be excessively volatile nor decompose excessively under the conditions, should not extensively detrimentally alter the physical characteristics of the fabric, and should not introduce undesirable poisonous characteristics to the fabric.

The acid introduced imparts swelling, and mildew resistance. If the particular acid has flame-resistance imparting properties, this additional property also results. phosphoric and sulfuric acids impart this property.

Since the acids are strong in nature it is desirable, for purposes of controlling the reaction,

to introduce a nitrogen containing organic buf- V fering agent or agents into the aqueous solution or mixture of the acid, said agent or agents to be present in suflicient quantities to produce a pH of from approximately 2 to approximately '7 on the cured cloth, the preferred range being from 3 to about 6, when tested with indicator solutions. By a buffering agent, we here mean such a substance or substances which will com- 1 pete with the cellulose for the acid, thereby mini- For example, orthomizing the likelihood of objectionably tendering the material, particularly with respect to tensile strength. These substances are basic in nature, 1. e., they are basic to the strong acid in solution. Weak bases, such as urea, biuret, dicyandiamide, strong bases, such as guanidine, guanylurea, biguanide, and mixtures of strong and weak bases, may be employed. The weak bases are used in substantial excess as they do not sharp- 1y affect pH. Where a strong base is employed, 1. e., one in which a change in quantity produces a marked change in acidity of the solution, it is desirable to use in addition a weak base such, for example, as urea and biuret. Other strong bases not of an organic character may be used to adjust the pH, i. e., reduce the acidity of the solution if too acid, such as, for example, soda ash, sodium hydroxide and borax, it being necessary in such cases to see that sufficient acid groups are available to insure combination with the cellulose and that suflicient buffering agent, such as urea,- is present to prevent undesirable degradation of the cellulose. If the solution is slightly alkaline, the pH may be adjusted with an acid, such, for example, as acetic acid. The pH of the solution isusually higher than the pH of the cured fabric, ordinarily pH higher or more. The general requirement of the pH of the solution is that it shall be such that the above set forth pH on the cured cloth is achieved during the curing. The pH usually drops during the curing.

Generally, we prefer a ratio by weight, of or ganic base to acid in the solution, of very rough- 1y 2 to 1, but the ratio may vary widely as shown in the examples.

Insofar as a buffer is concerned, the general requirements are that it shall be such as to compete with the cellulose for the acid, shall be soluble to some extent in water and shall not cause objectionable degradation of the fabric, under the condition of the process.

Salts and substitution products of the bases mentioned above may be employed, provided they are of the general characteristics just described.

Where flame-resistance is also desired, the nitrogen incorporated due to the presence of the buffering base, supplements the flame-resistance imparting acid.

Although swelling of the fabric will be obtained when fabrics treated as above described are immersed in water, it is possible to obtain a great variance in this property. As will be shown, the conditions of the curing and also the chemical composition of the mixture on the cloth affect the results obtained. Thus, in Example 1, it will be shown that a formula using urea and orthophosphoric acid gives swelling which varies substantially with change in curing conditions, while, as shown in Example 2, a formula using urea, dicyandiamide, guanidine carbonate and orthophosphoric acid gives a swelling which varies comparatively little with change in curing conditions. The former formula when curing under the most suitable conditions, gives excellent swelling, while the latter gives relatively poor swelling under any condition, although practically the same type fabrics were employed.

Since the swelling tendency is a direct function of the quantity of water absorbed by the fibers, the difference in effect is apparently due to the smaller quantity of water absorbed by the latter complex. In the case of urea and orthophosphoric acid, the complex is more simple 2'95 than in the case.i.of1,.,the ..urea,. 'dicyandiami-de, 1. .guanidine carbonate and orthophosphoriagacid, fffthe use ,of. which resultslin more complex compounds.

v.jiAlthougli the. presenceof a .nitrogenousbui- 1 felting, agent. is,'.desired".to control "the reaction upon the cjell'ulose;jthe presence of alarge' quantity of nitrogen in the finished fabricfthezcured, washed fabric) is not. essentiallunless"substantialfiame-resistance is also desired; in which'case nitrogen'in the complex .isL ery useful. .Thisis "shown in Example 3;"when a :soaping with soda .ash'and. soap-removed nearly allofithe nitrogen, "leaving". only a .very small percentage. Theresulting fabric, (after coating," gave avery satis- :f-actory water .bag' and the fabric :its'elf hadexcellent swellingproperties.

From the foregoing; titrappears that the' swell ing propertyiis toxbe attributed primarily torthe acid'groups in the" complex, and, dependingnpon the bases employed, this property is affected'very little or not at all wherethe base is urea and is, reduced, somewhat .where mixtures of various ".bases are. employed; ,In'ithe former case, there is acombinationwhich favors. a. maximumwater absorption, whileinthe'latter, case the combi ,..n'ation. is 'less' favorable. .JIhe resulting fabric,

I after coating, gave a verysatisfactory water bag andLthe fabric'itself had excellent swelling properties.

In the accompanying drawings, Figs: 1 and 2 are illustrative curves, the first of-nvhichisdntended primarily. to; showsthemeffect. of time: of cure and the second of which -is; intended"- pri marily to show the effect of formulationmand" fabric.

Figure 3 is a simple conventional showing of a=-water bag" made of the fabric of our invention and having a lid-*made 'ofthe-same fabric.

Examples 1- and 2* also-demonstrate the-importance ofthe kind or constr-uction of fabric --which should-be employed. In Example lyan ordinaryherringbone twill of about 8 ozs. to the "sq: yd: was treated, and notwithstanding that the-fibers showed-marked swelling-properties, the fabric was too-loosely-wovento make a'really satisfactory-water bag. The'leakage is-to great and the "evaporating surface toosmall. on the other hand; in Example 2, '-the-cloth-- is slightly 1 heavier and somewhat: better 'results'wou-ld' have 'been*'o'btained had the :formulation'" beemmore favorable: to :sw'elling.

The-timeand temperatureof curing are very important and the degree-of swelling is in part dependent uponv these factors. The preferred time and temperatures are; of: course related to several factors such as th'e type of acid used, the pH on the cured fabric, the type of fabric and the nitrogenous buffering, agent or agents used.

Generally, ;the.' lower .the 3 temperature the longer the time and the higher the temperature the shorter the time, other factors being equal. We prefer to usetemperatures from 250 F. to 400 F. and time. ofcure from 120 minutes to 30 seconds, the preferred range being 300 F. to 350 *Frand thepreferred time-from 8-minutes to l "minute. Above 'theselimits there is, great" danger that the fabric will be-excessively 'deg'raded particularly'with respect to strength. 'Nosatisfactory commercial results are obtained-below these limits in-reasonable time. It is to be un 'derstood thatswfllingltakes place b6tW6S1'lTWidG limits 'inthe time "and temperature, as wvill be shown, but to get maximum swelling adfinite tors: remaining Ethe same. As an "example-we "I'mayuse urea and" orthophosphoric acid,- on her- "ringbone twill "(Example --We then-find that a Zminute' curegives-moderate swelling; a

3 minute'curegives-excellent swelling; and a 7'minutecure, poor swelling. This'is shown by "the curve ofFigure 1. For'each temperature, the curve-will show a time peak, i. e., critical "point, at which maximum swelling is obtained, 10 and the time required to reach the peak will vary with the temperature, the lower the tem- *-perature the longer the time and vice versa. In Figure 2, the curve is relatively flat in com- --parisong butwould still show a peak if the time of heating were" extended. With anygiven set of conditions, it can readily be determined by "test when-the peak, i. e., maximum swelling is achieved. In this connection, it is to be observed that when imparting substantial flame-resistance go 'as well as swelling, a similar curve for flame- -resistance is obtained, but the flame-resistance curve and theswelling curve do not coincide. "The peak of flame-resistance is achievedwith a longer time 'of curing. In other words, maximum'fiame-resistance can only be achieved at someexpense in swelling property, and bestresults, where both properties are desired, can only be had by compromise.

"We'preferto use 'urea and orthophosphoric acid since these chemicals areinexpensive and easily available and give excellent results, and 'weprefer to cure'the fabric as above described to get the maximum degree of swelling.

For the particular purpose of water bag fabrics, weprefer to use a heavyptightly woven fabric as preventingobjectionable leakage and as presentcing'adequate'evaporating surface. We have ob- :tainedgood-results on certain cotton ducks, twills rand oxfords of *this general" character.

Heavyxtightly woven fabricssuch as; for extamplahard'texture or hard twist. ducks from the "#2/0itype to-the #11 type weighing from 32 ozs. 1--toT'l3 ozsqper square yard,:also regular cotton zduck from No. 3/0 to-No; 11 weighing from 34 ozs. .1m l3x'ozsuper;squareyard are-suitable and have beencused extensively. in' large scale production "with results ranging from excellent to satisfac- L-tory. Weprefer the closely woven heavy type of fabrics (up. to and inclusive of #l0rduck) since vthey1present ailarge evaporating surface to the atmosphere and "therefore give greater" cooling :sieffectiand :when swollen-prevent objectionable .a'sleakage. vOthr types of: duck fabrics meeting the r-a'bove-lspecifications may heused with success, as

1 imayxeloselyc woven-rsateens and twills of about -iwlfiaozs::per:,squaresyardweight" or heavier. It is evidentthatithisprocess can alsoqbex applied to -4other::celluloseifibrous materials such as, forexarample, linen 1 and rayon; provided the weave -01 construction is about of the weightrange given.

1 "Bi lie; best-results are obtained-with material comoperable to*-#l' to #8 hardtwist. duck. The others -.mentioned may 3.1801138: used,. butit is. desirable -;.for. .opti1num.-results..to additionally treat the .lighter. weight fabricsas hereinafter pointed. out. H In othentypesof finishes. previously described, makingeusevof a. plain cotton fabric and sizes having water swelling properties, it. is necessary to desize and scour the. fabric to' obtainthe de- 7o"sired water'absorbency. This is notthecase withourinventi'on'where a greyunscoured fab- 'ric may be-used to obtaingood-re'sults; since the A greyfabric 1 after treatment" has excellent absorbency.

l condition" is "desirableduring curingrotherfac i 76 We-prefer," howeverrto 'have the cloth desized and scoured to produce a good absorbent fabric prior to treatment. Mercerization, asstated, is beneficial and may be resorted to. The finish may be applied to undyed, dyed or printed fabrics, depending upon the effect desired.

The application of the solution follows conventional textile methods of application such as, for example, padding, printing and spraying. The fabric is then dried to remove the moisture and this is followed by the curing. The drying and curing may be combined into one operation. After curing the cloth may be given a washing to remove excess soluble chemicals.

Successive applications of size may be resorted to in order to obtain sufficient chemicals in the fabric. It is desirable, after the curing and washing, to have present in the fabric from approximately 8% to approximately 30% of chemicals. Higher solids take-on may be had but this does not appreciably improve the results, and lower take-on is apt to give unsatisfactory results. While the composition and the amount of chemical on the cloth is important, the concentration of the solution itself is unimportant, as either a single application or a succession of applications of the solution, with intermediate dryings, may be resorted to. In the case of a single application, with the squeeze set to give an approximately 100% solution pick up, the concentration should be such as to give an initial chemical take-on for the curing of from about 16% to 60% which would give an ultimate takeon in the cured, washed fabric from about 8% to about 30% as above indicated.

If the right cloth, say #4 hard twist duck, or its equivalent, is properly processed, a fabric may be obtained which will produce a satisfactory water bag, without further treatment, such as coating. It is, as previously indicated, beneficial in lighter weights, such as a #11 duck or similar weight cloth, or even somewhat heavier, to further treat by coating or impregnating the cured fabric, preferably the former, with a sizing solution to further reduce the passage of water through the bag. The sizing or coating mixture may be any material which will impede the passage of water through the fabric. We may mention, for example, waterproofing agents, waxes, plastics, resins and gums. We prefer to coat this water impeding material on one side (the inside) of the fabric since this procedure enables us to maintain a large surface on the outside of the bag and therefore, greater cooling efficiency. We may use film forming as well as swelling materials, such as, for example, vinylacetate-chloride copolymer, vinyl butyral, acrylate, polyethylene, rubber, polybutene, nitrocellulose, cellulose acetate, in fact, any of the textile coating materials well known in the art may be used as long as they impede the passage of water through the fabric and are not excessively water soluble. Some of these materials may be plasticized to obtain a satisfactory flexibility. Again, in this case the plasticizers used should not be excessively water soluble. They produce a discontinuous film, but nevertheless they reduce the size of the interstices by adding to the thickness of the yarn components of the fabric.

Materials which swell in water may be applied either alone or in conjunction with other materials, such as plastics. For example, methyl cellulose, polyvinyl-alcohol, gums, starch and alginates. The use of such swelling materials to impede the water is practical but not essential, since 8 if the proper fabric is used, suificlent swelling takes place in the fabric itself.

The great difference between our process and other processes now on the market lies in the fact that we obtain satisfactory results essentially by making the fabric swell in itself, while all other processes make use of sizing materials to cause the swelling while the fabric itself remains practically unaltered.

As previously stated, the alteration in the cellulose renders the fabric much less susceptible to attack by fungi and this is a very valuable aspect of the fabric. Since the chemicals are combined with the cellulose, they are not soluble in the cold water and, therefore, the mildew-resistance obtained is durable and without danger of poisoning so prevalent among the regular mildewproofing agents. Here, again, it is the acid and not the nitrogen in the finished goods which gives mildew-resistance. The fabric is also creaseresistant.

Emample 1 To show the high degree of swelling obtained, a desized, scoured and dyed herringbone twill fabric (37, 72/46, 1.83 yds./lb.) having an original air porosity or air permeability of 7 seconds, when tested on the Gurley Densometer (using .10 sq. inch die, 5 oz. cylinder and 300 cc. of air) was impregnated (single application) with the following mixture:

400 parts urea 200 parts orthophosphoric acid (75%) 200 parts water followed by drying. Difierent sections were cured at different times, keeping the temperature constant at 320 F. After a thorough washing in hot water to remove all soluble material, the fabrics were dried. Samples of these fabrics were wet with water and then placed in a hydrostatic test machine and the time for the passage of 50 cc. of water was measured, this bein again a measure of the degree of Swelling. The longer the time the greater the swelling. The results given in the table below, and shown on the graph of Figure 1, show the phenomenal swelling of the treated fabric in water. An untreated fabric when placed in the machine allowed the water to pass through so rapidly (a few seconds) that no accurate measurement could be obtained.

Time for gi passage of 50 cc. Water Min. Sec. 2. 0 54 3.0 101 3. 5 81 4.0 33 4. 5 23 5.0 17 7.0 ll

, was about 1 to about 8 v Q .jfi i s m wli tmq e ft t i esistla but-would have .sornewhat less swelli M Y Ex m e;

To show the somewhat less degree of swelling...

ObtainedQWhen-thechemical -constitution...of' the mix is changed,---a' sample: ;of. -.37.f.-r 88/56. 11321 ydsa/lm desize'd. scoured andcdyed twillt'fabricn having an original air porosity .or.air'..-permeabile ity of 10 'sec. when tested on: the. vvGrurlbyeDerlsom-- plication') with the following mixture q.

eter (as describedh was impregnated; (single .ap;-..

9.0 a s rt ,li ss eiil ifi (75%) arts a erw l followed by drying, Different sections'were cured at tr ntfimee eepin hei nm i 1 m stant fat 320; F." After thorough washingdn-hot water; the fabrics were dried? Samples *ofthose bfi s.WQIQ Q l-W ih. We. hydrostatie machine "and the time for the passage of 5000. ofwater noted) The results-when. cornpared with the previous example -indicate that despitefthle sli ig htl'y denser'clth the time was much less thanbfore-Qthus showing that a' ma ler sears? f swe lin wee h treated;cloth however; allowed the passage of 50 cc; of water within 4 sec.-,' proving'that a definite" we eshad i ke w- The...ratio of acidgroups .to pyranQs e. units for the.3..-minute, .cure was about .1.to .about Q, andfon the; Thminute. curewas about .1 to. about 5,;

The. results also. show that. :witlrth' forrnula the-degreeiofiswelling is .notinfluenced as by variance in time and, that the n 1ore comp compound zp ducedi e .1 fever; water h9i j may to the, sametextent as in Example 1.;

remrl fi.

poured, dyed #6. hard twist duck was sized it flie qllowi is ifi e d W se? 390.0 parts polyphosphoric acid 450.0 parts guanid'ine carbonate 1500.0. parts ,urea- ,37 -fl 1 r s ete f.

h iablr q wa ured. t 39? i5fm k s nd thee secur d] n was and "59% ash'i o w by a thoxpusewa hin ehqt wee s-s t mega s s and placed ;in the followed by drying. The fabric .was then cured water-to remove all solublematjerial. The .fab-j ric was made intoaiwatergibags.without,..further:;;

emulsion:

water bag ate-i9; a pbteinedi,

and dried.

The waterbags prepared from this fabric were mcas'gobd.

Example 4 scoured, bleached and .d W

fabric was impr-egnated'tho ture of:

excellent. Witho'ut thei coatihg thel'resultsFare 400 parts urea 200 parts orthophosphoric acid (75%) 200 parts water 3 i1'1inutes'at-3303 Feiand finally Jwashedimhot A regular cotton ducky, fabric weighing; :15.20 ozs. per square yard was padded thrcught 500 parts fluorophosphoric acid 1320 parts urea l000 parts water..-

washed to remove excess chemicals;.

li tly no e. i i? The fabric was then coated very side with the following solution An eigc I 19.0 parts Vinylite VYNW 171.0 parts Vinylite VYNS 147.0 parts Flexol D. O. P. 40.0 zerts. metby e ohu ylz.ketqn t eth liie ylq iqs par s toluene 1141. arts This demonstrates the use of a non-swelling coating, the closing of .thefabric, being obtained entirely. .loy the .swelli or va rr'isofzwljiilcli I I in diameterbvbating.

Example 6 A #8 hard twist duck breviously' scoured and dyed was treated with the following mixtur'e'j'?" 300.0 parts conc. sulfuric acid 65.0 parts polybutene,

108.0 parts triethanola 4588.0 parts-toluene 4334.0 parts water The resulting fabric which demonstrates the use of a small quantity of swelling material (methyl cellulose) in the coating mixture gave a very good water bag.

Example 7 A #4 hard twist duck, scoured to insure good absorbency, was impregnated with the following mixture:

100.0 parts orthophosphoric acid 65.0 parts dicyandiamide 75.0 parts acetamide 210.0 parts water 450.0 450.0 parts dried and a portion then cured 4 minutes at 335 F., followed by washing in warm water. The results were excellent.

' Another portion was coated on one side with a stearamidomethylpyridinium chloride wax emulsion prepared by mixing together:

100.0 parts stearamidomethylpyridinium chloride 12.5 parts guanidine carbonate 11.2 parts acetic acid (70%) '76.0 parts polyvinyl alcohol 704.0 parts water The resulting fabric gave exceptional results.

Example 8 A secured and bleached #4 hard twist duck fabric was thoroughly impregnated with the following solution:

300 parts urea 100 parts biuret 200 parts orthophosphoric acid (75%) 200 parts water 800 parts followed by squeezing, drying and curing 3 minutes at 340 F. The cloth was then washed thoroughly in hot water to remove soluble materials and then dried.

Water bags made from this fabric were found to give excellent service.

Example 9 A scoured and dyed #4 hard texture duck was impregnated with the following solution:

500.0 parts urea 500.0 parts water 120.0 parts fluorosulphonic acid and then dried.

One part of the fabric was curved 90 minutes at 250 F. and the second part 2 minutes at 400 F. After washing and drying the fabrics were given a light coat on one side with an acrylate resin emulsion. The resulting fabrics had good swelling properties and produced very satisfactory water bags.

Example 10 A grey, unbleached and unscoured, regular #10 duck (l5 ozs./yd. was thoroughly impregnated with the following solution:

200.0 parts orthophosphoric acid (75%) 400.0 parts urea Water to make 120 gals.

and squeezed so that the solution pick-up was by weight and then dried. The fabric was cured 4 minutes at 320 F. and washed in warm water, soaped in a dilute slightly alkaline soap solution, washed with water and dried.

The resulting fabric had excellent swelling properties and produced very good water bags without the application of sizing agents.

It will be seen from the foregoing that the weak bases, and more particularly urea, are to be preferred as interfering the least with the swelling effect imparted by-the acid.

We'have found that water bags made from 010th prepared as above described, work very satisfactorily under normal temperature and atmospheric conditions encountered over the United States and elsewhere, the rate of transpiration, i. e., of passage of water through the bag to the exterior, being for all practical purposes approximately equal to the rate of evaporation. Of course, under abnormal conditions such as at times of extreme relative humidity, the rate of evaporation will drop relatively.

The fabric of the invention suffers no obj ectionable loss of tensile strength from the treatment.

The #4 hard twist duck used had the following approximate specification: width 36, count 34/24, weight 24 ozs./yd.

The #6 hard twist duck had the following approximate specification: width 36", count 42/28, weight 20.5 ozs./yd.

The No. 10 regular duck had the following approximate specifications: width 36", count 45/32, weight 15 0zs./yd.

Another way of describing fabrics suitable for the purpose is by reference to air porosity and weight. Thus, for example, for initial cloth suitable for the purpose without any coating, an air porosity on the Gurley Densometer (under the conditions heretofore mentioned) of from 25 seconds and up, with a weight of from about 13 ozs. per sq. yd. and up, may be used, the higher the second value and the weight, the better the results. One may go to about as low as an air porosity of 10 seconds, with a weight of about 8 ozs. per sq. yd., where the coating is also employed.

In some .cases it may be desirable, after the curing and washing, to impart a mechanical finish such as schreinering or calendering to make the fabric somewhat more dense; Similarly, especially where the fabrics are of the lighter weight and less dense construction, mechanical treatment such as schreinering can be advantageously employed after the curing and washing but before the coating is applied.

While we have indicated a solid concentration of 60% on the fabric to be cured, it will be understood that this may be exceeded, but the excess represents wastage as no material benefits result from the use of quantities in excess of 60%.

Using a solution formulation of phosphoric acid and urea for illustrative purposes, about the low limit of acid in the finished fabric in the washed state, for satisfactory results, is about 1 acid group to about 25 pyranose units. One may go much higher, in fact as high as possible, but extremely high ratios represent the use of unnecessary amounts of chemical without corresponding improvement in results.

We claim:

1. A water bag composed of cotton cloth having a construction and weight of the general order of those of #2 to #10 hard texture duck, and having acid groups chemically combined with the cellulose in a ratio of not less than 1 acid group to 25 pyranose units, said cloth being characterized by a rate of transpiration approximately equal to the rate of evaporation, under atmospheric conditions ordinarily encountered, and by mildew-resistance and by a capacity 'for water swelling materially greater than that of cotton.

2. A water bag composed of cotton cloth having an air permeability ranging approximately from 25 seconds and up in the Gurley Densometer (using .10 sq. in. die, 5 oz. cylinder and 300 cc. of air) and a weight of from 13 ozs. and up per sq. yd., and having acid groups chemically combined with the cellulose in a ratio of not less than 1 acid group to 25 pyranose units, said cloth be ing characterized by a rate of transpiration approximately e'qual to the rate of evaporation, under atmospheric conditions ordinarily encountered, and by mildew-resistance andby a capacity for water swelling materially greater than that of cotton.

3. A water bag composed of cotton cloth having a construction and weight of the general order of those of #4 to #8 hard texture duck, and having nitrogen containing acid groups chemically combined with the cellulose with a ratio of not less than 1 acid group to 25 pyranose units, the said cloth being characterized by a rate of transpiration approximately equal to the rate of evaporation under atmospheric conditions ordinarily encountered, and by mildew-resistance and ill flame-resistance and by a capacity for water swelling materially greater than that of cotton.

4. A water bag composed of cotton cloth having a construction and weight not substantially I less dense and lighter than those of #4 hard textur duck, and having acid groups chemically combined with the cellulose in a ratio of not less than 1 acid group to pyranose units, said cloth being characterized by a rate of transpiration approximately equal to the rate of evaporation, under atmospheric conditions ordinarily encountered, and by mildew-resistanceand by a capacity for water swelling materially greater than that of cotton.

5.- A water bag composed of cotton cloth having a construction and weight of the general or-'- der of those of #2 to #11 hard texture duck, and having acid groups chemically combined with the cellulose in a ratio of not less than 1 acid group to 25 pyranose units, and the cloth being coated on one face with a discontinuous substantially non-Water soluble coating and being characterized by a capacity for water swelling materially greater than that of cotton.

6. A water bag composed of cotton cloth having a construction and weight not substantially less dense and lighter than those of #10 hard combined with the cellulose in a ratio of not less than 1 acid group to 25 pyranose units, said cloth being characterized by a rate of transpiration approximately equal to the rate of evaporation, under atmospheric conditions ordinarily encountered, and by mildew-resistance and by a capacity for water swelling materially greater than that of cotton.

7. A water bag composed of cotton cloth having a construction and weight of the general order of those of #2 to #10 hard texture duck and having acid groups chemically combined with the cellulose in a ratio of not less than 1 acid group to 25 pyranose units, said cloth being characterized by a rate of transpiration approximately equal to the rate of evaporation under atmospheric conditions ordinaril encountered and by mildew resistance and by a capacity for water swelling materially greater than that of cotton.

CHARLES J. KINTNER. WILLIAM Po HALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,068,362 ORiely July 22, 1913 1,127,384 Adams Feb. 9, 1915 2,012,159 Eward Aug. 20, 1935 2,049,217 Mennier July 28, 1936 2,089,697 Sroebe Aug. 10, 1937 2,098,082 Bowen et al Nov. 2, 1937 2,099,363 I-Ieckert Nov. 16, 1937 2,174,534 Shipp Oct. 3, 1939 2,225,589 Haussmann et al. Dec. 17, 1940 2,233,475 Dreyfus Mar. 4, 1941 2,286,726 Gordon June 16, 1942 2,302,107 Dattow Nov. 17, 1942 2,332,047 Bock et al. Oct. 19, 1943 2,401,440 Thomas et al June 4, 1946 2,467,792 Wenzel et a1 Apr. 19, 1949 2,504,124 Hicks Apr. 18, 1950 FOREIGN PATENTS Number Country Date 479,753 Great Britain Feb. 7, 1938 510,199 Great Britain July 28, 1939 547,846 Great Britain Sept. 15, 1942 OTHER REFERENCES S. R. Merrill et al.: American Cotton Handbook, published by American Cotton Handbook Company (New York, 1941).

Ser. No. 233,292, Schubert et al. (A. P. 0.), published May 4, 1943. 

